In order to prevent soil and groundwater pollution, ensure the sustainablity of soil and groundwater use, and fulfill the regulations of Soil and Groundwater Pollution Remediation Act, the Environmental Protection Administration (the EPA) initiated the Project of Investigating Soil and Groundwater Pollution at Gas Stations(the Sixth Phase)- Plans A and B in 2010, including completion of 400 gas stations investigation. MWH Taiwan carried out Plan A, covering Central and Northern Taiwan, while Sinotech Engineering Consultants, Ltd. (Sinotech) carried out Plan B, covering Central and Southern Taiwan.
Plan A was aimed to investigate the level of soil and groundwater
pollution at 191 gas stations in Central and Northern Taiwan. The findings from the investigation will be used as references for the subsequent pollution control. The investigation was implemented in the following three stages:
1. Stage 1: Detected and measured the fuel vapor of soil gas monitoring well.
2. Stage 2: Based on the results of Stage 1, sampled and analyzed soil and groundwater collected from simple wells at the gas stations with high pollution potential.
3. Stage 3: Installed standard monitoring wells at the gas stations with high pollution potential, to sample and analyze groundwater in which the pollutants are beyond the control standard from Stage 2 investigation.
For Stage 1, 191 gas stations were investigated, covering basic functional tests of 3,240 soil gas monitoring wells, measurement of fuel vapor concentration by using Lower Explosive Limit (LEL), Photo Ionization Detector (PID), and Flame Ionization Detector (FID), and measurement of soil vapor of 40 samples by using PID and FID, and Gas Chromatography (GC) analysis of 209 soil vapors. Through the evaluation of the fuel gas concentration detected by soil gas monitoring wells, the results indicated that there were 1 gas station with the highest pollution potential (Class A) and 1 gas station with the second highest pollution potential (Class B).
For Stage 2, 41 gas stations in total were investigated, including:
- 17 stations in total which were classified as Class A and Class B due to their high fuel gas concentration, and were classified as Level 1 and Level 2 on GC analysis;
-19 high –pollution-potential gas stations under the project of the EPA, 2009, “Inspection of facilities for preventing the pollution of groundwater bodies and monitoring equipment at gas stations and providing the owners advice on reporting monitoring results through internet”;
-5 gas stations in central region on national freeway.
The investigation tasks of 41 gas stations in Stage 2 consisted of detection and analysis of 151 soil and 100 groundwater samples from simple wells. The findings showed that among those 41 stations, there were 17 stations with soil pollutant concentration exceeding standard, and another 17 stations with groundwater pollutant concentration over the control standard as well.
For Stage 3, we further analyzed the 17 gas stationsin, in which 10 out of 17 consists groundwater pollutant concentration over the control standard.
It was concluded that there are 18 gas stations which are either with over-standard soil pollutant concentration, or with over-standard groundwater pollutant concentration:
- 8 stations with over-standard soil pollutant concentration
- 1 stations with over-standard groundwater pollutant concentration
- 9 stations with over-standard soil and groundwater pollutant concentration
In sum, all of these 18 polluted stations should be remedied in accordance with the Soil and Groundwater Pollution Remediation Act. In addition, to serve as references for the environmental protection agencies in the follow-up administrative control measures, the
correlation analyses of the basic information of the investigated-gas stations, groundwater pollution control facilities, periodic declaration reports, and pollution potential were also conducted.